Just get this and get Windows XP home edition....
You will go overbudget by about $25, but its worth it...
it matters dual channel vs no dual channel, makes a big performance boost. I tried using 2x 512 vs my 1gb stick and it makes a HUGE diffrence... and this was on my socket a build i had 2 years ago.
OR.. Get this..
Rosewill R6422 SL ATX Mid Tower Computer Case+350W Power Supply - Retail $22.99 + 11 Shipping. instead of the case Chozart had suggested, get rid of the power supply, and get this.
And your set. $43 Shipped.
New total: 528 .. argh, still overbudget, but you get a very very good and stable power supply.